[mothered]

Obviously I won’t actually know if it’s been opened or not when they receive it back so always a a bit worried about doing it with a dummy as they’ll see straight asay it’s not real

I fully agree.

That's also my concern with every sealed box method- If the return Is opened, regardless of what Item was substituted, It will fail. For this reason alone, It's paramount to not demonstrate "any signs of Inconsistencies" with the packaging. Unless they have reason to, companies don't usually open boxes sealed by the manufacturer, otherwise It will render the Item a second-hand unit.